Pretty sure Horde have the same kind of portals, but I'm speaking from an Alliance PoV. For the sake of speed, I took the Hyjal portal from Stormwind to battle Brok. Then I took the portal back to SW, and went into Deepholm to battle Bordin Steadyfist. Again, I took the portal back to Stormwind and went out to Twilight Highlands. After defeating Goz Banefury, again, I took the portal to and from Stormwind, this time to Uldum. After I defeated Obalis, I hearthed. This seems like the fastest way if you're looking to just knock out the achieve.

TL;DR - Brok-> Bordin Steadyfist-> Goz Banefury -> Obalis

Comment by misiaq

Comment by ladymalora

I found Brok, but it won't let me fight him. He just says something to me, without the option of battling him. Is there something I have to do to unlock it? According to the achievement, I haven't battled him yet.